1. Field of the Invention
The present invention relates to a medium for culturing microorganisms. More specifically, it relates to a medium for examination of foods or the environment, which can be used to detect microbial contamination in foods or the environment more quickly than conventional standard media.
2. Description of Related Art
The conventional microorganism examination is carried out in the following manner. In the case of yeasts and molds, first a powder agar medium is dissolved, autoclaved and poured into Petri dish, which is then cooled and solidified to keep the surface dry. The predetermined amount of a test sample such as a homogenate of foods is applied on the above prepared agar medium and incubated at 25° C. for maximum 7 days, and the number of grown colonies is then counted. For enumeration of yeasts and molds in the environment, a predetermined portion of a test object is wiped with a cotton swab or gauze, and then any microorganism caught on the swab or gauze is washed with sterilized water to be suspended in the sterilized water. This homogenate is applied on the above prepared agar medium and incubated, and then the number of grown colonies is counted. In the case of total viable counts, first a powder agar medium is dissolved and autoclaved, and is then kept at approx. 45° C. A predetermined quantity of this agar medium is poured into sterilized Petri dish, and mixed with 1 ml of a test sample such as a homogenate of foods, which has been pre-poured in the Petri dish, and is then solidified. Incubation is carried out at 35° C. for 2 days, and the number of grown microorganism colonies is counted. Thus, the conventional method of examining microorganisms requires 7 days of incubation for yeasts and molds enumeration, and 2 days for total viable count.
As a culture medium that can detect growing microorganism colonies by using a chromogenic reagent, a medium using an indole derivative is described, for example, in Reference 1, and a medium using TTC (2,3,5-triphenyl tetrazolium chloride) as a tetrazolium salt is described, for example, in Reference 2.
Reference 1: Japanese Tokkyo Kokai Koho (Un-Examined Patent Publication) 2001-231541
Reference 2: Japanese Tokkyo Kokai Koho 2001-245693